- still needs style
- will cache for 10 seconds

per feedback, use reverse() when generating callback urls. Also generate thumbnails when ingesting static images. We'll need these handy for the CMS UI.

Support asset library references in CapaModule. Also some code refactoring/cleanup. Preparing for review and submit

* for more context, see https://basecamp.com/1892446/projects/631155-devops/messages/4719963-strange-caching

Fix JSON postback error where the content-type header line can contain more info than just the application/json descriptor. Now we just to a compare on the start of the header value.

Fix JSON postback error where the content-type header line can contain more info than just the application/json descriptor. Now we just to a compare on the start of the header value.

* also replace the external-auth-related popping up of the signup form with jquery.
Presumably it takes care of the browser specific stuff.

* in-progress to fixing support for ':' in url_names

missed instance of login link which should have been behind DISABLE_LOGIN_BUTTON

- add a check for the feature flag before trying to save user info to the service

functionality - grade dump and download as csv, manage staff list,
force reload of course from xml

Added OPENID_PROVIDER_TRUSTED_ROOTS django setting. It should be a
list of glob matching patterns: ['*.cs50.net', '*.other.net']

Also did some minor refactoring and cleanup.

- provider placed behind separate feature flag
- domain of openid consumer displayed in login page
- added logging for successful login, changed log messages to include
  "OpenID"

- endpoint supports both SReg and AX
- identity taken from edX username
- sreg fullname and ax http://axschema.org/namePerson taken from edX
  name
- sreg email and ax http://axschema.org/contact/email taken from edX
  email